AC Heating Element for Aerosol Devices
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Solution Overview
Problem
Existing aerosol-generating devices face challenges with fragile ceramic heating elements that break easily and metal elements with low DC resistance leading to inefficient heating and power losses.
Innovation Solution
An electrical heating assembly using an AC driving current with a frequency between 500 kHz and 30 MHz, coupled with a robust metal heating element made of ferromagnetic or ferrimagnetic materials, which increases effective resistance and heating efficiency while reducing the risk of breakage and power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a ceramic heating element is used, then heating capability is achieved, but the element becomes fragile and prone to breakage
Solution Approach 1:
The patent changes the material parameter from ceramic to metal, fundamentally altering the mechanical properties while maintaining heating capability through AC current application
Solution Approach 2:
The patent applies periodic AC current at specific frequencies (500 kHz to 30 MHz) to the metal heating element, utilizing the skin effect to achieve effective heating while maintaining material integrity
2Reliability
If a metal heating element is used, then mechanical robustness is improved, but DC resistance is too low resulting in inefficient heating
Solution Approach 1:
The patent changes the electrical parameter by switching from DC to AC current and optimizes the frequency parameter (500 kHz to 30 MHz) to utilize the skin effect, which increases effective resistance and heating efficiency
Solution Approach 2:
The application of periodic AC current at optimized frequencies creates skin effect that concentrates current near the surface of the metal element, effectively increasing the resistance and heating efficiency
3Temperature
If DC current is used to heat the element, then heating is achieved, but power losses are high and heating results are unreproducible
Solution Approach 1:
The patent replaces DC current with periodic AC current at specific frequencies (500 kHz to 30 MHz), which utilizes the skin effect to reduce power losses and improve heating efficiency
Solution Approach 2:
The patent changes the electrical current type from DC to AC and optimizes the frequency parameter to achieve better heating efficiency and reproducibility with reduced power losses
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a robust and efficient heating process with self-limitation to prevent overheating, ensuring consistent aerosol generation and extended device lifespan.
Implementation Method 1
The heating element is operatively coupled with the control circuit and configured to heat up due to Joule heating when passing an AC driving current—provided by the control circuit—through the heating element
Implementation Method 2
AC currents mainly flow at the 'skin' of an electrical conductor between an outer surface of the conductor and a level called the skin depth. The AC current density is largest near the surface of the conductor, and decreases with greater depths in the conductor. With increasing frequency of the AC driving current, the skin depth decreases which causes the effective cross-section of the conductor to decrease and thus the effective resistance of the conductor to increase
Implementation Method 3
an aerosol-forming substrate which is capable of forming an inhalable aerosol upon heating is brought in thermal proximity of or even direct physical contact with a resistive heating element
Data Source
AI summary
The present invention relates to an electrical heating assembly of an aerosol-generating device for resistively heating an aerosol-forming substrate. The heating assembly comprises a control circuit configured to provide an AC driving current. The heating assembly further comprises an electrically resistive heating element for heating the aerosol-forming substrate. The heating element is operatively coupled with the control circuit and configured to heat up due to Joule heating when passing an AC driving element provided by the control circuit current through the heating element. The present invention further relates to an aerosol-generating device for use with an aerosol-forming substrate, wherein the aerosol-generating device comprises a heating assembly according to the invention. The invention also provides a method for resistively heating an aerosol-forming substrate by passing an AC driving current through a resistive heating element.